QueenC_87
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Q1) What is a liquid that is not soluble in water. However when dissolved in ethanol and heated with silver nitrate solution it gives a cram coloured solid? It is a secondary species????

Q2) This liquid produces white steamy fumes when put into contact with solid PCL5. It changes the colour of acidified potassium dichromate solution from orange to green. It is a primary species???
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Claree
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(Original post by QueenC_87)
Q1) What is a liquid that is not soluble in water. However when dissolved in ethanol and heated with silver nitrate solution it gives a cram coloured solid? It is a secondary species????

Q2) This liquid produces white steamy fumes when put into contact with solid PCL5. It changes the colour of acidified potassium dichromate solution from orange to green. It is a primary species???
Q1) When bromide ions react with acidified silver nitrate you get a cream precipitate.
Haloalkanes are generally insoluble in water and soluble in organic solvents. Haloalkanes cannot H-bond with water. In non-polar solvents the attraction between the haloalkanes and the solvent is a strong (or stronger) than the attraction of solvent for solvent particles. Hence I think you want a secondary haloalkane ("bromo"alkane).
Spoiler:
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Could be 2-Bromopropane?


Q2) alcohols or carboxylic acids containing C-OH react with PCl5 and misty fumes of HCl are produced.
acidified potassium dichromate will oxidise a primary or secondary alcohol.
You are told it is a primary species, so you want a primary alcohol that is a liquid at room temperature.
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Ethanol
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QueenC_87
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(Original post by Claree)
Q1) When bromide ions react with acidified silver nitrate you get a cream precipitate.
Haloalkanes are generally insoluble in water and soluble in organic solvents. Haloalkanes cannot H-bond with water. In non-polar solvents the attraction between the haloalkanes and the solvent is a strong (or stronger) than the attraction of solvent for solvent particles. Hence I think you want a secondary haloalkane ("bromo"alkane).
Spoiler:
Show
Could be 2-Bromopropane?


Q2) alcohols or carboxylic acids containing C-OH react with PCl5 and misty fumes of HCl are produced.
acidified potassium dichromate will oxidise a primary or secondary alcohol.
You are told it is a primary species, so you want a primary alcohol that is a liquid at room temperature.
Spoiler:
Show
Ethanol


You are a star!!! can you help me with two more

1) A liquid that is not soluble in water. It burns to give a yellow flame with very little soot. It does not remove the colour from bromine water- the water stays orange???

2) A liquid that gives a positive 2.4 dinitrophenylhydrazine test- yellow/orange crystals are formed. It reacts with Fehlings solution to give a red solid???


You are a life saver if you can answer just them two. Thank you so much!
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QueenC_87
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(Original post by Claree)
Q1) When bromide ions react with acidified silver nitrate you get a cream precipitate.
Haloalkanes are generally insoluble in water and soluble in organic solvents. Haloalkanes cannot H-bond with water. In non-polar solvents the attraction between the haloalkanes and the solvent is a strong (or stronger) than the attraction of solvent for solvent particles. Hence I think you want a secondary haloalkane ("bromo"alkane).
Spoiler:
Show
Could be 2-Bromopropane?


Q2) alcohols or carboxylic acids containing C-OH react with PCl5 and misty fumes of HCl are produced.
acidified potassium dichromate will oxidise a primary or secondary alcohol.
You are told it is a primary species, so you want a primary alcohol that is a liquid at room temperature.
Spoiler:
Show
Ethanol
Please
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Claree
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(Original post by QueenC_87)
You are a star!!! can you help me with two more

1) A liquid that is not soluble in water. It burns to give a yellow flame with very little soot. It does not remove the colour from bromine water- the water stays orange???

2) A liquid that gives a positive 2.4 dinitrophenylhydrazine test- yellow/orange crystals are formed. It reacts with Fehlings solution to give a red solid???


You are a life saver if you can answer just them two. Thank you so much!
Sorry I was at a concert this evening!

1) Non sooty flame means low C ratio, so it's not an aromatic compound I.e. it's not benzene. Not decolorising bromine water means there are no C=C double bonds. I guess it will be an alkane then (non polar so doesn't dissolve in water) that's a liquid e.g. propane. Propane burns with a yellow flame.

I'm on my phone, will reply to the other q when I get home.

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QueenC_87
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(Original post by Claree)
Sorry I was at a concert this evening!

1) Non sooty flame means low C ratio, so it's not an aromatic compound I.e. it's not benzene. Not decolorising bromine water means there are no C=C double bonds. I guess it will be an alkane then (non polar so doesn't dissolve in water) that's a liquid e.g. propane. Propane burns with a yellow flame.

I'm on my phone, will reply to the other q when I get home.

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You are absolutely amazing!!! thank you. The second question gives me a hint that it is a four carbon compound so I have Butanal. Will you let me know when you get a chance if this is correct? Thank you xxx
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Gibber96
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(Original post by QueenC_87)
You are a star!!! can you help me with two more

1) A liquid that is not soluble in water. It burns to give a yellow flame with very little soot. It does not remove the colour from bromine water- the water stays orange???

2) A liquid that gives a positive 2.4 dinitrophenylhydrazine test- yellow/orange crystals are formed. It reacts with Fehlings solution to give a red solid???


You are a life saver if you can answer just them two. Thank you so much!
Positive test with 2,4-dinitrophenylhydrazine indicates a C=O from an aldehyde or ketone (not from a COOH group), and reacting with Fehlings means it is oxidised to give a carboxylic acids. Ketones can't be oxidised by Fehling's, so the answer is any aldehyde e.g. ethanal
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QueenC_87
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(Original post by Gibber96)
Positive test with 2,4-dinitrophenylhydrazine indicates a C=O from an aldehyde or ketone (not from a COOH group), and reacting with Fehlings means it is oxidised to give a carboxylic acids. Ketones can't be oxidised by Fehling's, so the answer is any aldehyde e.g. ethanal
The answer should contain four carbon atoms therefore the answer would be Butanal?
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Gibber96
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(Original post by QueenC_87)
The answer should contain four carbon atoms therefore the answer would be Butanal?
That's right!
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QueenC_87
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(Original post by Gibber96)
That's right!
Woo hoo. I'm new to organic chemistry, only just started this module two weeks ago. It's taking time to get my head round it but I am getting there! Thank you both for your help! Much appreciated. xxxxxxx
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Claree
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(Original post by QueenC_87)
You are a star!!! can you help me with two more

1) A liquid that is not soluble in water. It burns to give a yellow flame with very little soot. It does not remove the colour from bromine water- the water stays orange???

2) A liquid that gives a positive 2.4 dinitrophenylhydrazine test- yellow/orange crystals are formed. It reacts with Fehlings solution to give a red solid???


You are a life saver if you can answer just them two. Thank you so much!
2) The first test shows a C=O in aldehyde or ketone, the second test narrows it down to an aldehyde. As it's a liquid, it could be e.g. ethanal.

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QueenC_87
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(Original post by Claree)
2) The first test shows a C=O in aldehyde or ketone, the second test narrows it down to an aldehyde. As it's a liquid, it could be e.g. ethanal.

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Thank you so much! I really appreciate the help you have given me, particularly for giving me an explanation and not just an answer. It helped my understanding. xxxx
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Claree
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(Original post by QueenC_87)
Thank you so much! I really appreciate the help you have given me, particularly for giving me an explanation and not just an answer. It helped my understanding. xxxx
You're welcome!!

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